Normal fetal development is directly dependent on adequate transfer of oxygen and nutrients across the placenta. Inadequate placental transfer of oxygen results in fetal hypoxemia that has been associated with alterations in fetal physiology and fetal structure. Low levels of fetal oxygenation represent a major cause of intrauterine growth restriction (IUGR), an abnormality that leads to low birth weight (which accounts for 10 percent of all pediatric health care costs in the United States). At present, no effective method exists for noninvasive in vivo assessment of placental or fetal umbilical vein oxygenation. They hypothesize that MR Oxygenation Imaging can provide a noninvasive in vivo measure of placental oxygenation which can be used to identify a hypo-oxygenated placenta. MRI has proven to be a safe and robust technique for anatomic imaging of the fetus and placenta. Moreover, MRI has been shown to be an effective noninvasive method to assess in vivo oxygenation. While techniques for MRI of oxygenation have been applied effectively elsewhere in the body, they have not yet been demonstrated in the placenta. The goal of this R21 is to determine the feasibility of MR oxygenation imaging in the placenta. Specific aims for the project are: (1) to develop and characterize a reproducible MR-compatible model of placental hypo-oxygenation in a sheep model and (2) to evaluate the utility of MRI to detect differences in response of normal and compromised placenta to maternal hyperoxygenation therapy. The group at Beth Israel Deaconess Medical Center has been instrumental in the development of MR of the fetus and has extensive experience in oxygenation imaging. This project promises significant clinical impact -- availability of a noninvasive in vivo method to evaluate placental oxygenation could provide a sensitive and clinically relevant measure of placental function, aiding in the earlier and more specific diagnosis of IUGR, allowing for appropriate intrapartum care.